1. Field of the Invention
This invention relates to a process for preparing lactams. In particular, the present invention provides a process for selectively reacting a novel 1-hydrocarbylamino (or heteroatom-substituted hydrocarbylamino); 1,1-dicarboxylic acid, alkylesters; 1-hydrocarbyl (or heteroatom-substituted hydrocarbyl) carboxylic acid, alkyl ester methane, as the salt of an acid having a pKa of 0 or more, to provide novel lactams wherein one or both hydrocarbyl moieties are incorporated into the lactam ring. Preferably, The selectivity of the reaction is controlled by either cyclizing the novel salts, in the absence of a base, or cyclizing said novel salts, in the presence of an amount of base substantially equivalent to said acid. That is, the acid moiety of said novel salt promotes the reaction whereby both hydrocarbyl moieties are incorporated into the ring, while the presence of a base promotes the reaction whereby only one hydrocarbyl is incorporated into the ring. Therefore, reaction at neutral or slightly basic conditions provides improved selectivity to lactams having a smaller ring size, while the acid-catalyzed reaction increases the selectivity to lactams having a larger ring size.
2. Description of the Art
Lactams are cyclic amides having many uses as intermediates for the preparation of polymers, medicinals, etc. In particular, in medicinal uses, certain lactams have been found to enhance the transdermal penetration of various physiologically-active compounds into the tissues and blood stream of an animal, e.g. a human. See, for example, U.S. Pat. Nos. 3,989,816; 4,316,893; 4,310,525; 4,422,970; and 4,405,616; wherein lactams, in particular, having 1-n-alkyl azacycloalkan-2-ones, having a ring size of from 5 to 9 members are shown to enhance the transdermal penetration of physiologically-active materials. It has been found that both the size of the ring and the length of the n-alkyl group affects the transdermal penetration-enhancing properties of the 1-n-alkylazacycloalkan-2-ones disclosed in these patents. Thus, it would be desirable to have a process for selectively varying both the ring size and the length of the n-alkyl group as well as preparing novel substituted lactams for penetration enhancement. Lactams are also useful in the preparation of nylon 6-type polymers wherein the properties thereof may be systematically modified through the regulation of the nature and position of the lactam substituent. See, for example, C. G. Overberger et al., Journal of Polymer Science, Vol. 10, 2265-2289 (1972).